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Dissolution and precipitation processes (saturation indices). The ‘Solmnique’ computer program has been used to calculate the saturation indices (SI) for the studied groundwater samples in relation to the relevant phases in the system (calcite, dolomite, gypsum, anhydrite and halite). The SI values determine the extent to which a groundwater has reached chemical equilibrium with the minerals within the aquifer matrix (SOLMINEQ.GW 1999). The results in Tables 6 and 7 show that Quaternary and Miocene groundwater samples have –ve saturation index values with respect to Gypsum, Halite and Anhydrite. This reflects the undersaturation and the continual dissolution of these salts on aquifer contact. On the other hand, about 88% of both the Quaternary and Miocene samples have +ve saturation index values with respect to Dolomite, while 68% of the Quaternary and 63% of the Miocene samples have +ve saturation index values with respect to Calcite. These +ve saturation index values reflect the oversaturation with respect to Calcite and Dolomite and the tendency of the groundwater to precipitate them on rock contact.

Table 6

Results of calculated SI from ‘Solmnique’ program for Miocene aquifer samples and their descriptive statistics

Sample IdDolomiteCalciteGypsumHaliteAnhydrite
0.66 −0.12 −0.19 −4.35 −0.47 
1.26 0.18 −1.02 −4.73 −1.31 
1.36 0.15 −0.10 −4.00 −0.34 
10 −0.52 −0.64 −0.32 −4.20 −0.61 
12 0.75 0.03 −0.89 −4.71 −1.18 
31 2.02 0.51 −0.43 −4.30 −0.72 
32 3.60 1.30 −0.21 −4.20 −0.50 
33 0.20 −0.50 −1.22 −4.30 −1.50 
Av. 1.17 0.11 −0.55 −4.35 −0.83 
Min. −0.52 −0.64 −1.22 −4.73 −1.50 
Max 3.60 1.30 −0.10 −4.00 −0.34 
Sample IdDolomiteCalciteGypsumHaliteAnhydrite
0.66 −0.12 −0.19 −4.35 −0.47 
1.26 0.18 −1.02 −4.73 −1.31 
1.36 0.15 −0.10 −4.00 −0.34 
10 −0.52 −0.64 −0.32 −4.20 −0.61 
12 0.75 0.03 −0.89 −4.71 −1.18 
31 2.02 0.51 −0.43 −4.30 −0.72 
32 3.60 1.30 −0.21 −4.20 −0.50 
33 0.20 −0.50 −1.22 −4.30 −1.50 
Av. 1.17 0.11 −0.55 −4.35 −0.83 
Min. −0.52 −0.64 −1.22 −4.73 −1.50 
Max 3.60 1.30 −0.10 −4.00 −0.34 
Table 7

Results of calculated SI from ‘Solmnique’ program for Quaternary aquifer samples and their descriptive statistics

Sample IdDolomiteCalciteGypsumHaliteAnhydrite
0.26 −0.40 −1.54 −5.11 −1.83 
0.27 −0.38 −1.60 −5.28 −1.89 
1.63 0.40 −0.87 −4.89 −1.15 
0.53 −0.18 −1.18 −6.12 −1.50 
0.10 −0.42 −1.55 −5.80 −1.84 
1.69 0.44 −1.02 −7.44 −2.11 
11 1.56 0.32 −1.40 −5.27 −1.70 
13 1.53 0.36 −0.90 −4.70 −1.19 
14 1.75 0.67 −0.15 −4.98 −0.44 
15 1.27 0.17 −1.10 −5.42 −1.34 
16 −0.85 −0.91 −2.53 −6.40 −2.82 
17 −0.37 −0.63 −1.08 −6.08 −1.37 
18 −0.06 −0.47 −0.87 −5.60 −1.16 
19 1.19 0.14 −1.00 −5.50 −1.30 
20 0.77 −0.03 −1.26 −6.50 −1.55 
21 1.30 0.20 −1.39 −6.20 −1.68 
22 2.12 0.55 −1.50 −6.30 −1.28 
23 1.38 0.22 −1.15 −6.41 −1.44 
24 0.966 0.20 −2.40 −7.60 −2.70 
25 1.1 0.14 −1.20 −4.70 −1.20 
26 2.03 0.64 −2.50 −6.80 −2.50 
27 1.5 0.40 −2.60 −7.50 −2.60 
28 1.8 0.40 −2.90 −7.70 −2.90 
29 0.6 0.43 −0.92 −6.70 −0.92 
34 3.10 1.10 −1.70 −5.80 −1.90 
Av. 1.09 0.13 −1.45 −6.03 −1.69 
Min. −0.85 −0.91 −2.90 −7.70 −2.90 
Max 3.10 1.10 −0.15 −4.70 −0.44 
Sample IdDolomiteCalciteGypsumHaliteAnhydrite
0.26 −0.40 −1.54 −5.11 −1.83 
0.27 −0.38 −1.60 −5.28 −1.89 
1.63 0.40 −0.87 −4.89 −1.15 
0.53 −0.18 −1.18 −6.12 −1.50 
0.10 −0.42 −1.55 −5.80 −1.84 
1.69 0.44 −1.02 −7.44 −2.11 
11 1.56 0.32 −1.40 −5.27 −1.70 
13 1.53 0.36 −0.90 −4.70 −1.19 
14 1.75 0.67 −0.15 −4.98 −0.44 
15 1.27 0.17 −1.10 −5.42 −1.34 
16 −0.85 −0.91 −2.53 −6.40 −2.82 
17 −0.37 −0.63 −1.08 −6.08 −1.37 
18 −0.06 −0.47 −0.87 −5.60 −1.16 
19 1.19 0.14 −1.00 −5.50 −1.30 
20 0.77 −0.03 −1.26 −6.50 −1.55 
21 1.30 0.20 −1.39 −6.20 −1.68 
22 2.12 0.55 −1.50 −6.30 −1.28 
23 1.38 0.22 −1.15 −6.41 −1.44 
24 0.966 0.20 −2.40 −7.60 −2.70 
25 1.1 0.14 −1.20 −4.70 −1.20 
26 2.03 0.64 −2.50 −6.80 −2.50 
27 1.5 0.40 −2.60 −7.50 −2.60 
28 1.8 0.40 −2.90 −7.70 −2.90 
29 0.6 0.43 −0.92 −6.70 −0.92 
34 3.10 1.10 −1.70 −5.80 −1.90 
Av. 1.09 0.13 −1.45 −6.03 −1.69 
Min. −0.85 −0.91 −2.90 −7.70 −2.90 
Max 3.10 1.10 −0.15 −4.70 −0.44 

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